1. Field of the Invention
The present invention relates to a light scanning device.
2. Description of the Related Art
Conventionally, (for example, refer to a patent document 1: Japanese Patent Unexamined Publication 2006-39399) there has been a known light scanning device which is mounted in, for example, an image forming apparatus to scan to a photoconductive drum as a scanned member by deflecting on a rotational multifaceted mirror a laser light irradiated from a light source. In such light scanning device, normally, there is provided a first optical system and a second optical system between the light source and the rotational multifaceted mirror, and a third optical system is provided between the rotational multifaceted mirror and an outgoing slit through which the light goes out.
The first optical system is adapted to form the laser light outgoing from the light source into a parallel light flux. The second optical system is adapted to collect the laser light formed into the parallel light flux toward a sub-scanning direction which is perpendicular to a main scanning direction as a direction in which the scanning is performed, so that an image is formed linearly on the rotational multifaceted mirror. On the other hand, the third optical system has a function to render a scanning speed of the laser light scanned on the photoconductive drum and deflected by the rotational multifaceted mirror to be a constant speed, so that a dot-like image of the light deflected by the rotational multifaceted mirror is formed on the photoconductive drum.
Meanwhile, in the light scanning device, a laser scanning line may curve on the photoconductive drum in a sub-scanning direction in accordance with accuracy in assembling components (namely, generation of bowing). Here, the patent document 1 discloses that an fθ lens constituting the third optical system is rotated about a line which is parallel to the main scanning direction so as to adjust the amount of curving of the laser scanning line on the photoconductive drum.
When the fθ lens is rotated to adjust the amount of curving of the laser scanning line on the photoconductive drum like the case of the patent document 1, its rotation center is generally set at a center of the fθ lens, in other words, at a center between intersections at which an optical axis of the fθ lens intersects with an incident side surface and an outgoing side surface of the fθ lens. In the case where such configuration is adopted, the curving of the laser scanning line on the photoconductive drum can be improved when the fθ lens is rotated. However, the scanning line shifts largely in the sub-scanning direction.